Implantable medical devices (IMDs), such as implantable cardioverter-defibrillators, may detect a cardiac arrhythmia and provide various electrical therapies in response to detection of the arrhythmia. Therapies provided by an IMD in response to a detected arrhythmia may include anti-tachycardia pacing (ATP) therapy, cardioversion therapy, and/or defibrillation therapy, depending on the type of arrhythmia detected.
Some detected arrhythmias may be life-threatening. Ventricular tachycardia (VT) and ventricular fibrillation (VF) may be considered to be life-threatening arrhythmias. In examples where an IMD detects such a life-threatening arrhythmia, the IMD may provide a defibrillation shock to the patient's heart in order to correct the arrhythmia and return the patient's heart rhythm back to a normal rhythm.
An IMD may include components that are dedicated to producing a defibrillation shock in response to detection of a life-threatening arrhythmia. For example, an IMD may include high-voltage capacitors for storing electrical charge for subsequent delivery during a defibrillation shock. Additionally, the IMD may include a delivery circuit that transfers the electrical charge from the high-voltage capacitors to the heart. During operation, an IMD may typically monitor a patient's heart rate, or other parameters (e.g., morphology, onset, etc.) in order to detect an arrhythmia. If the IMD detects a life-threatening arrhythmia, the IMD may charge the high-voltage capacitors and control the delivery circuit to transfer the energy from the high-voltage capacitors to the patient's heart using either a biphasic or a monophasic waveform. Delivery of the defibrillation shock may terminate the detected arrhythmia and return the heart to a normal rhythm.